Method of producing certain commercial products from potash feldspar.



* rrE' STAs 'a'rnnr me EDWARD L. ANDERSON, F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO JOHN S.

SNYDER, 0F PITTSBURGH, PENNSYLVANIA.

METHOD OF PRODUCING CERTAIN COMMERCIAL PRODUCTS FROM POTASH FELDSPAR.

Llama-5.

No Drawing.

To all whomz't may concern:

Be it known that'I, ED ARD L. ANDERSON, a citizen of the United States, and resident ofv Pittsburgh, in the county of Allegheny and State pf Pennsylvania, have invented certain new and useful Improvements in Methods of Producing Certain Commercial Products from Potash Feldspar,of which the following is a specification.

The method of the present invention, While relating to the decomposition of insoluble alkaline minerals in general, has

particular reference to the decomposition of feldspar, and its practice in that connection is described herein. 7

While it has been known that silicates can be decomposed with a treatment ofhydrowith the water to form silicic acid and hydrofiuosilicic acid, the latter accumulating inthe solution in the presence of the amount of water required to keep the sulfates in so- This removes the hydrofluoric acid With the relution. from the sphere of action.

" action proceeding at atmosphereic pressure v likely be somewhat lower.

the working temperature could not exceed the boiling point of the mixture and would If the reaction is carried out at higher temperatures, the hydrofluosilicic acid decomposes and forms hydrofluoric acid and silicon tetrafluorid,l

both-of which are gases and would tend to escape from the solution.

What-is requiredin order to, utilize the hydrofluoric acid to the fullestextent is a set of conditions that will permit of the continuous decomposition of hydrofluosilicic acid into hydrofluoric acid and silicon tetrafiuorid which are not allowed to escape, the

silicon tetrafiuorid being decon'oposed by the I water to form silicic acid and hydrofluosilicic Specification of Letters Patent.

- Patented Mar. 7, 1916.

Application filed November 10, 1915. Serial No. 60,719.

acid, the latter undergoing the above decomposition again, and all the hydrofluoric same to. a temperature of say from 275 F. to 350 F. for maintaining a pressure of 50 to 7 5 pounds per square inch. To. this mixture is added an equivalent amount of sulfuric acid necessary to combine and form sulfates with the aluminum and potassium contained in the feldspar. In addition there is added to this mixture an amount of hydrofluoric acid equal to approximately five per cent. (5%) of the amount of sulfuric acid used or the chemical equivalent of fluorspar. In practice,- I have found that the percentage of hydrofluoric acid may be'varied between 2 and 10 per cent., the difference being that 1n using a lower percentage the operation requires 'a longer time for a-,complete reac- With the conditions above recited, in from eight. to ten hours.

tion. complete reaction may be had I have discovered that in order to accomplish complete decomposition of the feldspar with complete absorptionof all acid, the strength of the acid mustbe maintained. As the available amount of sulfuric acid decreases as the reaction" proceeds, I

I maintain the requisite strength by reducing the water content of the acid mixture, accom-plishing this by liberating steam therefrom. I find that if I libenate steam at the beginning of the process. a small amount of hydrofluoric acid aswell as silicon tetrafiuorid escapes, but if no steam is liberated until after-the reaction has continued for about two hours, there will be no escape of hydrofluoric acid or silicon tetrafluorid gases. This condition is due to the fact that all the fluorin has had time to combine with the bases to form fluorids. and under the maintained pressure at which the steam is released the hydrofluoric acid and silicon tetrafluorid are so combined with or held by the water and the bases that they, cannot escape.

Under the most favorable operating conditions the complete reaction may be carried out by using the theoretical amounts of feldspar and sulfuric acid. However, I have demonstrated that under conditions of. operation usually encountered thereaction may be more speedily accomplished by using an excess of feldspar. By so doing, the rapidity of thereaction is maintained until most of the sulfuric acid has been converted into sulfates ofthe metals, the remaining undecomposed feldspar being readily separable from the silica residue and hence available for subsequent decomposition.

During this operation the following reactions take place: The hydrofluoric acid acting on the feldspar .forms silicon tetrafluorid, aluminum fiuorid, potassium fluorid, Y.

and water. The silicon fiuorid combines with the water present to form hydrofluosilicic acid and silicic acid. The hydrofluosilicic acid in the presence ofwater and at the temperature and pressure existing reacts to form silicon tetrafiuorid and hydrofluoric acid. The silicon tetrafiuoridso formed is, in turn, convertedinto hydrofluoric acid and hydrofluosilicic acid, the latter again reacting as above. The aluminum fiuorids and potassium fiuorids are decomposed by the sulfuric acid and form aluminum sulfate, potassium sulfate, and hydrofluoric. acid. The silicic acid in the presence of Water and sulfuric acid is dehydrated, forming silicon dioxid.

The reactions involved are expressed in the following equations:

The mixture after theaction has finished may be filtered in suitable apparatus for the separation of the liquid from the residue. The insoluble residue-consists of pure silica, while the solution contains the sulfates of aluminum' and potash. together with a small amount of hydrofluoric and sulfuric acids. This solution may now be neutralized bv calcium hydroxid or other suitable agent during which operation the iron salts are precipitated, previously oxidizing the iron salts if necessary. From this point the procedure will depend on the products it is desired to obtain. For extion sets in. If it is desired to separate the.

potassium sulfate from the alumina, the dried mixture containing the potassium and aluminum sulfates may be calcined at a temperature sufiicient to decompose the aluminum sulfate only, forming alumina,

and leaving the potassium sulfate undecomposed. From this mixture the potassium sulfate maybe separated by simple leaching, followed by concentration by evaporation to the crystallizing point, giving as products potassium sulfate and alumina.

The method of the present invention e'nables me to produce valuable compounds from insoluble alkaline minerals, and particularly potash feldspar, in commercially economical quantities heretofore impossible.

I claim:

1. The process of treating feldspar or the like, consisting in subjecting feldspar to the action of a solution containing a decomposing agent together witha reagent for combining with the bases, and maintaining the mixture under pressure and at a temperature above its normal boiling point.

2. The process of treating feldspar or the like, consisting in subjecting feldspar to the action of a solution containing a decomposing agent together with a reagent for combining with the bases, the decomposing agent being less than the theoretical amount necessary to combine with all the bases, and maintaining the mixture under pressure and at a temperature above its normal boiling point. t

3. The process of treating feldspar or the like, consisting in subjecting feldspar to the action of a solution containing a decompos ing agent together with a reagent. for combining with the bases, and decreasing the water content of the acid solution as the.

decomposition proceeds.

4. The process of treating feldspar or the like, consisting in subjecting such mineral to the action of a solution containing a decom posing agent together with a reagent for combining with the bases, maintaining the mixture under pressure and at a temperature above its normal boiling point, and decreasing the water content of the acid solution asjthe decomposition proceeds.

5. The process of treating feldspar or the like, consisting in subjecting feldspar to the action of a solution containing a. decomposing agent together with sulfuric acid for like, consisting in subjecting feldspar to the combining with the bases, and maintaining the mixture under pressure and at a temperature above its normal boiling point 7. The process of treating feldspar or the like consisting in subjecting feldspar to the action of a decomposing solution containing hydrofluoric acid together with sulfuric acid tor combining with the bases, and maintaining the mixture under pressure and at a temperature above its normal boiling point.

8. The process of treating feldspar or the like, consisting in subjecting feldspar to the action of a solution containing a decomposing agent together with a reagent for combining with the bases. the amount of feldspar subjected to said solution being in excess of the theoretical amount which the solution will decompose, and maintaining the mixture'under. pressure and at a temperature above its normal boiling point.

9. The processof treating feldspar or the like, consisting in subjecting feldspar to the action of a solution containing a decomposing agent together with a reagent for combining with the bases, the amount of feld spar subjected to said solution being in excess of the theoretical amount which the solution will decompose, maintaining the mixture under pressure and at a temperature above its normal boiling point, and de creasing the water content of the acid solution as the decomposition proceeds.

10. The process of treating feldspar or the like, consisting in subjecting feldspar to th action of a solution containing a decomposing agent together with a reagent for combining with the bases, maintaining the mixture under pressure and at atemperature above its normal boiling point. and neutralizing the mixture to precipitate the iron salts.

In testimony whereof I aflix my signature in presence of two witnesses.

EDW'ARD L. ANDERSON.

Witnesses J. M. NEsBIT,

JOHN S. SNYDER. 

